It has been customary in the past to make whitened or otherwise pigmented polyvinyl chloride polymers or compositions using titanium dioxide as a whitener. The appearance of such polymers or compositions is measured relative to the overall appearance or look of the material, the yellowness, and the opacity of the material.
In the past, the main additive used in PVC known to produce useful hiding power (i.e., opacity and whitening) has been titanium dioxide. This has effectively presented a monopoly for the producers and distributors of this composition. Since the supply of titanium dioxide is, at times, less than the demand, it is an advantage to find a substitute for titanium dioxide as a whitener and/or opacifying agent. Attempts have been made in the past to find such substitutes. For example, carbon black has been used for its opacifying characteristics. However, carbon black presents the disadvantage that it discolors, i.e., darkens, the compositions in which it is used and makes it difficult to achieve a white or lightly-tinted composition. In the paint and paper industry in particular, hollow plastic microspheres have been used, but these whiteners and/or opacifying agents do not stand up to processing conditions which are used for polyvinyl chloride-type compositions.
U.S. Pat. No. 3,827,901 (Griffin et al, Aug. 6, 1974) relates to a composition of matter which is useful as a pigment composition for the paper industry. The composition is water-insoluble and comprises an intimate mixture of titanium dioxide and a calcium-aluminum-silicate composition in which the amount of titanium dioxide employed is from 0.6 to 4 parts for each part of the calcium-aluminum-silicate composition.
U.S. Pat. No. 4,078,941 (Bundy et al, Mar. 14, 1978) relates to a high bulking clay consisting essentially of selected flocculated ultrafine particles of clay coated with a member from the group consisting of polyfunctional amines and long chain amines.
U.S. Pat. No. 4,525,518 (Kostansek, Jun. 25, 1985) relates to pigments useful as primary extenders in exterior grade latex formulations. The pigments are composed of particles of calcined clay, substantially all the particles of which are finer than about 44 microns, and having an average particle size, equivalent spherical diameter, within the range of about 3 to 10 microns, most preferably within the range of about 4 to 8 microns.
U.S. Pat. No. 4,677,022 (Dejaiffe, Jun. 30, 1987) relates to a method of producing lightweight bodies having a glossy exterior which are suitable for use as modifiers, enhancers, fillers, extenders, and opacifiers in polymeric formulations. The reference also relates to the lightweight bodies themselves and to plastic composites in which those lightweight bodies are incorporated.